Simple GR(1) spec is identified as not GR(1)

[5nizza]

Consider the following specification.

$ cat gr1_bug.tlsf 
INFO {
  TITLE:       ""
  DESCRIPTION: ""
  SEMANTICS:   Mealy
  TARGET:      Mealy
}

GLOBAL {
  PARAMETERS { }
  DEFINITIONS { }
}

MAIN {
  INPUTS { r; }
  OUTPUTS { g; }

  INITIALLY { }
  PRESET { }

  REQUIRE { }
  ASSERT { g; }

  ASSUME { G F r; }
  GUARANTEE { }
}

It is clearly a GR(1) spec. However, the tool claims it is not.

$ syfco ./gr1_bug.tlsf  -gr
NOT in the Generalized Reactivity fragment: ./gr1_bug.tlsf

As a result, it cannot be converted into slugs format:

$ syfco ./gr1_bug.tlsf  -f slugs
"Conversion Error": not in GR(1)
The given specification is not in GR(1), which is neccessary to convert to the slugs format.